Calculating device for teaching arithmetic



United States Patent O CALCULATING DEVICE FOR TEACHING ARITHMETIC Irwin E. Cohn, Leominster, Mass., and Howard Healey, Hollis, N.H., assignors to Great American Plastics Co., Nashua, N.H., a corporation of Massachusetts Application May 9, 1958, Serial No. 734,348

2 Claims. (Cl. 35-9) The object of this invention is to provide an improvement upon the structure of addition and multiplication calculating devices particularly adapted for children, as in the minor school grades, and a structure which can be molded entirely, or almost entirely, from plastic. By means of the invention, the primary structural element may be molded in one piece of plastic, and hence is inexpensive, in such form that the movable elements may be very quickly assembled, and held in position by applying a single cover plate.

The said primary housing member is so designed that when the transverse rows of apertured slide bars are to be assembled they merely require longitudinal edge to edge abutment as to each group, and hence can be laid down, being held in slide relation by said mutual edge abutment, and by the cover plate. The apertured slide bars are operated by inward manual movement, and the combination of a simplified spring arrangement controlled in position only by the housing and the apertured slide bars themselves, greatly aids the simplicity and ease of assembly. Thus, there are two laid down spring members, consisting of spring strips, each with two rows of cutouts, with the metal bent downwardly in each row, as engaging lingers for the apertured slide bars.

The invention will be described with reference to the accompanying drawing, in which,

Fig. 1 is a schematic View to illustrate the primary casing element and the method of assembly, there being shown the two spring elements, the marked sheet, and four of each group of apertured slide bars, and in the order of their assembly from bottom to top;

Fig. 2 is a plan view of the assembled structure looking downward upon the front face thereof;

Fig. 3 is an enlarged fragmentary vertical section on the line 3 3, Fig. 2;

Fig. 4 is a fragmentary enlarged vertical section on the line 4 -4, Fig. 2;

Fig. 5 is a fragmentary corner horizontally sectioned on the line 5*-5, Fig. 3.

Referring to the drawings and particularly to the lower portion of Fig. 1, it will be seen that the casing consists of a unitary plastic body in rectangular form having outer side walls at 1. Within the casing are four walls 2 which have a double purpose. They serve as supports for apertured slide bars, and two of said walls 2 serve both as stop members which limit the inward movement of the slide bars and also serve as housings for the especially constructed spring members.

The bottom wall 3 of the said casing may be reinforced by the integral struts 4. The struts 4 also serve a useful purpose in supporting the numeral card 5 over 2,910,786 Patented Nov. 3, 1959 ICC which the apertured slide bars, arranged in two groups, are laid. In the present embodiment each group has l2 slide bars, bars of one group being indicated at 6, and bars of the second group being indicated at 7. At 8 are shown the two spring strips, each strip having cuts and spring elements bent therefrom, the cuts being in two rows and the elements of one row being bent reversely to those of the second row to provide ngers 9.

As shown in Fig. 4, each apertured bar is formed with a stop at 7x to limit its inward movement, and each bar at its rear end is formed with a shoulder at 10 for abutment by an appropriate spring linger 9.

In assembling the elements the two rows of apertured slide bars, consisting of a lower group of 12 bars and an upper group of l2 bars at right angles therewith, will be placed in position on the outer and inner walls 2 and in such position that the outermost bars of both groups will have edge abutment with corner walls at 11 and 12 respectively. The two spring strips are then pressed in position so that their lingers will engage the shoulders 10 of the apertured slide bars and those shoulders will be pressed inwardly and into contact with the outer faces of the inner walls 2, so that the front or finger ends of the slide bars will be projected outwardly of the casing. Of course the number sheet or plate 5 will iirst be placed on the struts 4.

The cover plate 14 may then be placed in position. At its corners it is formed with depending posts 15 apertured and threaded at their lower ends to receive screws 16, Fig. 5, rising upwardly through apertures in the bottom corners of the casing 1.

It will be assumed that in the present embodiment the device is for multiplication. Thus in Fig. 2 the left hand slide bar at 11 has been pressed inwardly and the top slide bar opposite the numeral 10 has been pressed inwardly to determine 1l 10, the result being shown in Fig. 5 as 110. Itis obvious that the number board 5 may contain modified indicia for other calculation purposes.

It will be understood that various modifications may be made in the form and arrangement of the elements, without departing from the spirit of the invention. Thus the bottom wall 3 may be made separate from the remaining part of the casing, or it may be made integral therewith. In Figs. 3 and 4 the bottom wall is shown with its struts 4, which lie marginally, in abutment with casing walls 2, and hence the bottom wall with its struts is detachable. Therefore by pivoting or otherwise enabling outward movement of the bottom wall, an initial number card may be removed and a different card placed in position. For example, the initial card may be for multiplication and the second card for subtraction, etc.

Having described our invention, what we claim and desire to secure by Letters Patent is as follows:

1. In a structure for calculating devices, a unitary molded casing, rectangular in form, and having marginal walls and at least two inner walls spaced therefrom and providing two chambers, the upper edges of said inner walls being adapted as supports, two superimposed groups of slide bars having said support as a rest, the bars of each group being parallel, and the bars of each group being individually provided with a row of apertures, the bars of one group extending at right angles to those of the second group having ends projected outwardly from side walls of the casing, the slide bars of each group being in mutual longitudinal edge abutment, spring means normally holding the' sliderk bars outwardly in such position thatunapertured areas of. the bars prevent!visualization to below the bars, a removable closure wall for the base of the casing, and means carried by the wall for a sheet printed with spaced indicia, said spring means being disposed in said chambers, and a cover plate for the casing and formed with rows of apertures.

2. A structure for calculating devices constructed in accordance with claim 1, in combination with inner walls at the corners of the casing and forming corner chambers, depending? posts carried by thek coverv plate projecting downwardly into said corner chambers of the casing,

and releasable means carried by the base of the casingv for attachment to said posts.

References Cited in the le of this patent UNITED STATES PATENTS 

